Firstly, thank you to all involved for your help in resolving this issue.
For information, it related to two R7008SB receivers that I bought second hand from a modelling colleague. However he is way up another level from me and flies large complex jet aircraft with the result that the receivers were set to another mode, possibly I think as he may have been using S Bus. All I did was to reset them back onto mode A and now they work perfectly. Thanks again.